Phase change inkjet printers typically receive phase change ink in a solid form. Blocks or ingots of solid ink are commonly referred to as ink sticks. Solid ink sticks are loaded into a printer and then melted to produce liquid, molten ink that is used to form images on print media. Phase change inkjet printers form images using either a direct or an offset (or indirect) print process. In a direct print process, molten ink is jetted directly onto print media to form images. In an offset print process, molten ink is jetted onto a transfer surface, such as the surface of a rotating drum, belt, or band. Print media are moved proximate the surface of the rotating drum in synchronization with the ink images formed on the surface. The print media are then pressed against the surface on top of the ink images to transfer and affix the ink to the print media.
Phase change inkjet printers are typically equipped with a drum maintenance system for applying release agent to the surface of the rotating member. The release agent is an oil, such as silicone oil or a similar type of substance. The drum maintenance system includes a reservoir that holds a supply of the release agent and a release agent applicator, such as a foam roller, configured to transfer the release agent from the reservoir to the surface of the drum. The release agent is applied to the surface of the drum to form a layer that receives the molten ink emitted by the inkjets. The layer of release agent facilitates the transfer of the ink image from the drum to media and helps prevent the adherence of ink to the drum surface during printing operations. Drum maintenance systems may be provided as customer replaceable units to facilitate the removal and replacement of the unit when the release agent in the reservoir is depleted.
Positioning any fluid containing structure, such as a reservoir of release agent, within the housing of a printer poses the risk of fluid leakage and spills onto the interior components of the printer. Due to the nature of the release agent fluid and the environment in which it is used, previously known leak sensors and detection systems are generally not suitable for use with drum maintenance systems of phase change inkjet printers. For example, some leak detection systems rely on the conductivity of leaked fluid to provide an indication of a leak condition. These sensors and systems are generally not capable of detecting or indicating leakage of a non-conductive fluid, such as release agent. Other types of leak detections systems utilize resistive sensing methods, float assemblies, or other methods that may be impractical to implement in customer replaceable drum maintenance systems due to complexity and/or cost.